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DOI: 10.1055/a-2658-0605
Significant Decrease in Scientific Performance after Completing Habilitation as an Academic Milestone: A Bibliometric Analysis of 742 Web of Science Profiles with Focus on Orthopedic and Trauma Surgeons
Wissenschaftliche Performance nimmt in Deutschland hochsignifikant nach der Habilitation ab: eine bibliometrische Analyse von 742 Web of Science-Profilen mit Fokus auf Orthopädie und UnfallchirurgieAuthors
Abstract
Purpose
Habilitation is a procedure by which one of the highest university degrees is achieved in the field of medicine in Germany. We hypothesize that this academic milestone represents an incentive for scientific productivity that drops off once a scientist has reached this career steep. This study aims to compare scientific performance of German scientists before and after completing this milestone with special focus on orthopedic surgeons and traumatologists (O&T).
Methods
Scientists who had completed their habilitation in human medicine were researched from public announcements in the period Jan–Dec 2018. The periods Jan 2016 to Dec 2018 and Jan 2020 to Dec 2022 were defined as pre- and post-habilitation phases, respectively. Scientific performance was calculated using normalized citation percentiles (NCPs) from author records in Web of Science. Association between sex, subject area, and change in performance were analyzed.
Results
NCP values of 742 scientists were analyzed showing a significant decrease after completing habilitation (p < 0.001). This applied to men and women (p = 0.015, p = 0.003) and non-surgical disciplines (p = 0.001), while surgical disciplines such as O&T only demonstrated a statistically non-significant decrease. Interestingly, women showed an increase in performance after habilitation in this male-dominated discipline at only 4.5% (2) females compared to males. Most scientists in the population experienced a decline in performance (53.9% [400]). This drop amounted to over 50% in 35.5% (142) of these cases. No association was found regarding gender or subject area.
Conclusions
Scientific performance seems to be incentive-dependent and significantly decreases after completing a career milestone in Germany. This decline is not statistically significant in O&T; women, who are strongly underrepresented, even show an increase in performance.
Zusammenfassung
Hintergrund
Die Habilitation ist ein Verfahren, mit dem in Deutschland einer der höchsten akademischen Titel im Bereich der Humanmedizin erreicht wird. Wir vermuten, dass dieser Meilenstein einen Anreiz für die wissenschaftliche Performance darstellt, die nach Erreichen dieser Karrierestufe nachlässt. Ziel dieser Studie ist es, die wissenschaftliche Performance deutscher Wissenschaftler vor und nach Erreichen dieses Meilensteins zu vergleichen; wurde ein besonderer Fokus auf Orthopäden und Unfallchirurgen (O&U) gelegt.
Methoden
Wissenschaftlerinnen und Wissenschaftler der Humanmedizin mit abgeschlossener Habilitation wurden aus öffentlichen Bekanntmachungen zwischen 01/2018 und 12/2018 recherchiert. Die Zeiträume zwischen 01/2016 und 12/2018 sowie zwischen 01/2020 und 12/2022 wurden als Prä- und Posthabilitationsphasen definiert. Die wissenschaftliche Performance wurde anhand von normalisierten Zitationsperzentilen (NCPs) aus Autorenprofilen von Web of Science ermittelt. Ein möglicher Zusammenhang zwischen Geschlecht, Fachgebiet und Leistungsveränderung wurde ebenfalls analysiert.
Ergebnisse
NCP-Werte von 742 Wissenschaftlern zeigten einen hochsignifikanten Abfall nach Abschluss der Habilitation (p < 0,001). Dies galt für Männer und Frauen (p = 0,015; p = 0,003) sowie für nicht chirurgische Disziplinen (p = 0,001), während chirurgische Disziplinen wie O&U nur einen statistisch nicht signifikanten Rückgang aufwiesen. Interessanterweise zeigten Frauen im Gegensatz zu Männern eine Perfomancesteigerung nach der Habilitation in dieser männerdominierten Fachdisziplin mit nur 4,5% (2) Frauen. Bei den meisten Wissenschaftlern kam es zu einem Performanceabfall (53,9% [400]). In 35,5% (142) der Fälle betrug dieser Abfall mehr als 50 %. Ein Zusammenhang mit dem Geschlecht oder dem Fachgebiet konnte nicht festgestellt werden.
Schlussfolgerung
Die wissenschaftliche Performance scheint anreizabhängig zu sein und nimmt nach Erreichen eines Karrieremeilensteins in Deutschland deutlich ab. Im Bereich O&U ist dieser Rückgang statistisch nicht signifikant; Frauen, die in diesem Bereich stark unterrepräsentiert sind, zeigen sogar einen Anstieg ihrer Performance.
Keywords
scientific performance - citation - normalized citation percentile - h-index - habilitationSchlüsselwörter
wissenschaftliche Leistung - Zitation - normalized citation percentile - h-Index - HabilitationIntroduction
Habilitation is a procedure by which one of the highest university degrees “PD” or “Priv.-Doz.” (Privatdozent) is achieved in the field of medicine in Germany [1] [2] [3]. This degree is an additional qualification at a higher level than the German doctoral degree, and it is usually a criterion for a full professorship within the German university system [1] [2] [3] [4]. Therefore, habilitation represents a milestone in an academic career. A habilitation candidate must fulfill a university’s set criteria of excellence in research, teaching, and education over a long period [1] [2] [3] [4]. Habilitation is awarded following a public lecture that the candidate delivers after the habilitation thesis has been accepted. Habilitation effectively includes the venia legendi (Latin: “permission to lecture”). The term habilitation is derived from the Latin term “habilis” (having sufficient ability to do or to conduct, being skillful) [5]. Consequently, it could be assumed that academic performance would increase or at least remain at the same high level once this higher qualification has been obtained if science is understood as an endogenous progress in which new, more meaningful findings are based on previous accumulated knowledge [6]. Recent evidence shows declining research productivity worldwide [6]. The volume of research papers published has skyrocketed over the past few decades, but the papers have become less novel compared to prior work [6]. The reasons for this phenomenon are unclear [6] [7].
We hypothesize that habilitation is a career milestone within the German university system, representing an incentive for scientific productivity that falls off once the scientist has achieved the object of this incentive.
This study aims to compare scientific performance among scientists of German universities using bibliometrics before and after completing their academic habilitation milestone.
This study has been authorized by the local ethical committee and was carried out in accordance with the Ethical standards of the 1964 Declaration of Helsinki as updated in 2004.
Scientific performance of all habilitation candidates of German universities in the field of human medicine from 2018 was compared before and after they completed their habilitation. The candidates were researched from announcements of a publicly accessible German university news portal and the biggest national medical journal [8] [9]. All candidates from the field of human medicine who had been announced as having completed their habilitation between January 2018 and December 2018 were included.
A three-year period between January 2016 and December 2018 was defined as the period before habilitation (prehab phase). The period after the habilitation (posthab phase) was defined as one year after the year of habilitation (2018) between January 2020 and December 2022. A one-year gap (2019) up to the habilitation year was deliberately chosen. This year was not evaluated to prevent lingering achievements during the prehab phase from distorting results from the posthab phase.
Scientific performance was calculated using established bibliometric parameters from author records in the Web of Science (WoS) [10]. Access took place between November 2023 and December 2023. The primary performance indicator was defined as the normalized citation percentile (NCP). NCPs are part of author impact beamplots [11]. An NCP indicates how a publication has performed relative to its peers, and how performance has changed over time, and therefore serves a normalized performance indicator [12]. NCP values are determined by comparing citations for a single publication to citation counts for all publications in the same year, subject category, and article type, and calculating the percentage of papers at each level of citation. Higher NCP values indicate better performance [12]. For example, a publication with a percentile of value of 99 is in the top 1% of most cited publications in the same article type, year, and subject category [12]. Changes in NCP values of 2016 and 2017 were compared against values of 2020 and 2021. The shortened period was selected because NCPs are not offered for the current and previous analysis year, and analysis was only possible up to 2021 at the time of the study design.
The number of publications, number of citations, and self-citations before and after habilitation were used as secondary performance indicators.
Sex of candidates was determined based on their first names. In addition to the affiliated university, the habilitation subject was categorized into surgical and non-surgical. The profile with the most entries was evaluated for each person with more than one author profile in the WoS. The number of publications, citations, and self-citations as well as h-index of the entire career period were also recorded.
Statistical analysis
Descriptive statistics were calculated. Interval and ordinal dependent variables were compared using the Mann-Whitney U test. NCP values from the two years in the prehab and posthab phases were pooled for group comparison. To calculate percentage change of NCP values, ordinal scaled NCPs in the two years of the prehab and posthab phases were first summed together. The NCP was raised from 0 to 1 for individuals without publications that year to avoid division by zero in the percentage calculation. Percentage change in NCP between the two phases was classified as follows: ≤−50%: strong; ≤−25%: moderate; < 0%: slight; 0%: no change; > 0%: slight; > 25%: moderate; > 50%: strong. Chi-squared test and Fisher’s exact test were used in analyzing the association between sex, subject area, and change in scientific performance. For this purpose, percentage change in NCP was calculated as categorial variable (decrease: < 0%; increase: ≥ 0%).
The confidence level (CI) was set at 95% (p < 0.05). Data analysis was performed using SPSS 26.0 (IBM, Armonk, New York) and Microsoft Excel 2019 (Microsoft Corporation, Redmond, Washington).
Results
The analysis encompassed 742 habilitation candidates announced from 36 universities. [Table 1] lists all the cities where the universities were located and the frequency distribution of scientists.
Men were represented more often than women by a majority of over two thirds (70% [519]). In surgical disciplines, this distribution was much more divergent with a significant association between sex, and subject area (p = 0.001; [Table 2]).
Scientific performance defined by NCP values decreased significantly after completing habilitation (p < 0.001; [Table 3]). This applied to both men and women (p = 0.015, p = 0.003; [Table 4]), but without any significant association between gender, subject area, and change in performance (χ² [1, n = 742] = 0.3, p = 1; [Table 2]).
However, women in surgical disciplines had lower rates of decline in performance than women in non-surgical subject areas (51.9% vs. 55.6%; [Table 2]).
Most scientists experienced a decline in performance (53.9% [400]). This decline was moderate to severe in a third of the total study population ([Fig. 1]). Performance increased in 39.6% (294) of the cases and remained at the same level in 6.5% (48) of the cases. [Fig. 1] shows frequency distribution of percentage change in NCP after completing habilitation.
Women published significantly less than men in the prehab phase and in total (p = 0.004, p = 0.034; [Table 4]). Nevertheless, they had similar mean values regarding number of citations, self-citations, and h-index, and they tended to be superior in their performance to the men in the prehab phase considering NCP median values. Their performance was even significantly higher in 2017, immediately before habilitation (p = 0.003). This advance diminished in the posthab phase, and their level of performance was comparable to that of men ([Table 4]). Secondary performance indicators – number of publications, number of self-citations – did not change significantly, but the absolute number of citations increased significantly in the posthab phase (p = 0.03; [Table 4]).
Orthopedic surgeons and traumatologists (O&T)
NCPs of 44 scientists were examined and showed a statistically non-significant decrease in performance after habilitation ([Table 5]). This decline was moderate to severe in 31.8% (14) of this subgroup.
Women were strongly underrepresented in this male-dominated discipline (4.5%, 2). However, similar to the total cohort, women published less than men but demonstrated nearly equal mean values regarding number of citations, and h-index. In addition, they tended to be superior in their performance to the men in both phases regarding NCP median values. In contrast to men, their performance even tended to increase after habilitation ([Table 5]).
Discussion
This is the first study to investigate scientific performance in the field of medicine among scientists of German universities with particular focus on their performance before and after finishing habilitation that functions as an academic milestone.
Our principal finding was that most scientists in Germany experienced a significant decline in scientific performance measured by an established bibliometric parameter after reaching that milestone. This decline in performance was moderate to severe in a third of the study population ([Fig. 1]). The primary performance indicator measured by using the normalized citation percentile decreased significantly, whereas secondary performance indicators, such as the number of publications and absolute number of citations, remained almost the same or increased significantly.
If science is understood as a progress in which new, more meaningful findings are based on previous ones [6] [7], and completing the habilitation is understood as just one milestone on this path that proves the ability to conduct independent research, then this observation is surprising. One would expect that academic performance would at least remain the same or increase further after habilitation. However, the opposite effect as observed – an decrease – supports our assumption that habilitation might be a career milestone within the German university system representing an incentive for scientific productivity that declines once a scientist has achieved the object of this incentive. These individuals might have primarily been interested in obtaining an academic title and could have influenced the results by representing a “low hanging fruits” mentality [6] [7]. However, other reasons are also conceivable. Personal circumstances could have been responsible for a temporary focus on other aspects of both private and professional life after reaching this career milestone. A temporary reduction in performance to recover intellectual creativity after the strenuous, time-consuming habilitation phase is conceivable.
Our finding that women tend to lose performance slightly more than men could underline this assumption. Women are known to be exposed to greater hurdles in their academic careers [13] [14] [15] [16], and the far lower number of habilitation candidates may reflect the additional burden of family planning in the following years [14] [15] [16]. Interestingly, we observed that women have published significantly less than men. Nevertheless, their mean values regarding number of citations and h-index were similar, and their performance measured by NCPs even tended to be superior to men in the prehab phase, which might confirm that a high quantity (number of publications) does not necessarily guarantee scientific quality.
Women’s performance in the year 2017, immediately before habilitation, was even significantly higher. This advantage flattened out after finishing habilitation, reaching a performance level comparable to that of men.
Women were strongly underrepresented (4.5%, 2) in the male-dominated O&T discipline, and tended to be superior to the men in both phases. In contrast to the men, their performance even tended to increase after reaching the academic milestone. Our observation that women surgical disciplines have a lower rate of performance loss than in non-surgical subjects, where the proportion of women is higher, suggests that this outsider role may be responsible for the result. However, our data subgroups are too different in sample size to allow a valid interpretation of these gender differences.
This study has several strengths. In addition to the large sample size, one of the strengths is the usage of NCPs as a performance indicator instead of the widely known h-index [11] [12] [17]. This index characterizes a researcher’s publication and citation counts to a single number that depends on career length and discipline as citation counts accumulate over time at rates that vary between research fields [12] [17] [18]. Therefore, it does not provide valid comparability between individuals and is mathematically inconsistent [12] [18].
Bornmann and Marx of the Max Planck Society introduced and developed usage of NCP containing impact beamplots for bibliometric data. The Institute for Scientific Information (ISI) has promoted NCP containing beamplots as an alternative to the h-index as they contextualize a researcher’s article to make them suitable for comparison; this reduces the risk of reliance on a single-point metric that lacks context and nuance, and performance changes can be evaluated over the course of a researcher’s career [12] [19] [20].
However, this study also has several limitations to consider. Firstly, the results are only transferable to a single country with a specific university system and only one discipline. Secondly, the results are limited by selection bias, as only a sample of scientists from 2018 was examined. Only scientists whose names had been publicly announced on the two accessed platforms could be included. Thirdly, the study period was short. Performance was examined just one year after the habilitation. It remains unclear whether and for how this decline would be observed over a longer examination period.
Conclusion
Scientific performance seems to be incentive-dependent and significantly decreases after completing a career milestone in Germany, but without any significant association between gender, subject area, and change in performance. In O&T, this decline is not statistically significant; women, who are strongly underrepresented, even tend to increase their performance.
Conflict of Interest
The authors declare that they have no conflict of interest.
Acknowledgement
We thank the team of Clarivate especially Mr. Alan Draganovic for enabling this study.
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References
- 1 Yildirim TM, Auffarth GU, Khoramnia R. [How to: the path to habilitation]. Ophthalmologie 2024; 121: 927-929
- 2 Weineck SB, Koelblinger D, Kiesslich T. [Medical habilitation in German-speaking countries: Quantitative assessment of content and elaboration of habilitation guidelines]. Chirurg 2015; 86: 355-365
- 3 Strauss M, Ehlers J, Gerß J. et al. [Status Quo – The requirements for medical habilitation in Germany]. Dtsch Med Wochenschr 2020; 145: e130-e136
- 4 Research in Germany. How to become a professor in Germany. Accessed October 01, 2023 at: https://www.research-in-germany.org/en/your-goal/postdoc/career-options-and-dual-careers/professorship.html
- 5 DWDS – Digital Dictionary of the German Language. Habilitation, die. Accessed October 01, 2023 at: https://www.dwds.de/wb/Habilitation
- 6 Park M, Leahey E, Funk RJ. Papers and patents are becoming less disruptive over time. Nature 2023; 613: 138-144
- 7 Kozlov M. ‘Disruptive’ science has declined – and no one knows why. Nature 2023; 613: 225
- 8 Deutsches Ärzteblatt. Accessed November 01, 2023 at: https://www.aerzteblatt.de/int
- 9 Forschung & Lehre. Accessed November 01, 2023 at: https://www.forschung-und-lehre.de/
- 10 Web of Science. Accessed February 08, 2024 at: https://www.webofscience.com/wos/
- 11 Szomszor M. The Web of Science Author Impact Beamplots: A new tool for responsible research evaluation. 01.03.2021 Accessed July 18, 2025 at: https://clarivate.com/academia-government/blog/the-web-of-science-author-impact-beamplots-a-new-tool-for-responsible-research-evaluation/
- 12 Adams J, McVeigh M, Pendlebury D. et al. Profiles, not metrics. January 2019. Accessed July 18, 2025 at: https://clarivate.com/academia-government/lp/profiles-not-metrics/
- 13 Yousaf R, Schmiede R. Barriers to women’s representation in academic excellence and positions of power. Asian J Ger Eur Stud 2017; 2: 2
- 14 O’Connell C, McKinnon M. Perceptions of Barriers to Career Progression for Academic Women in STEM. Societies 2021; 11: 27
- 15 Costello CA. Women in the Trenches: Barriers to Female Staff’s Advancement in Higher Education. Dissertations, Theses, and Masters Projects 2015.
- 16 Chao Q. The challenges facing female leaders in higher education – and how to address them. 12.02.2024 Accessed July 18, 2025 at: https://www.timeshighereducation.com/campus/challenges-facing-female-leaders-higher-education-and-how-address-them
- 17 Hirsch JE. An index to quantify an individual’s scientific research output. Proc Natl Acad Sci U S A 2005; 102: 16569-16572
- 18 Waltman L, van Eck NJ. The inconsistency of the h-index. JASIST 2012; 63: 406-415
- 19 Bornmann L, Marx W. Distributions instead of single numbers: Percentiles and beam plots for the assessment of single researchers. JASIST 2014; 65: 206-208
- 20 Bornmann L, Haunschild R. Plots for visualizing paper impact and journal impact of single researchers in a single graph. Scientometrics 2018; 115: 385-394
Correspondence
Publication History
Received: 09 April 2025
Accepted: 13 May 2025
Article published online:
21 August 2025
© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).
Georg Thieme Verlag KG
Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany
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References
- 1 Yildirim TM, Auffarth GU, Khoramnia R. [How to: the path to habilitation]. Ophthalmologie 2024; 121: 927-929
- 2 Weineck SB, Koelblinger D, Kiesslich T. [Medical habilitation in German-speaking countries: Quantitative assessment of content and elaboration of habilitation guidelines]. Chirurg 2015; 86: 355-365
- 3 Strauss M, Ehlers J, Gerß J. et al. [Status Quo – The requirements for medical habilitation in Germany]. Dtsch Med Wochenschr 2020; 145: e130-e136
- 4 Research in Germany. How to become a professor in Germany. Accessed October 01, 2023 at: https://www.research-in-germany.org/en/your-goal/postdoc/career-options-and-dual-careers/professorship.html
- 5 DWDS – Digital Dictionary of the German Language. Habilitation, die. Accessed October 01, 2023 at: https://www.dwds.de/wb/Habilitation
- 6 Park M, Leahey E, Funk RJ. Papers and patents are becoming less disruptive over time. Nature 2023; 613: 138-144
- 7 Kozlov M. ‘Disruptive’ science has declined – and no one knows why. Nature 2023; 613: 225
- 8 Deutsches Ärzteblatt. Accessed November 01, 2023 at: https://www.aerzteblatt.de/int
- 9 Forschung & Lehre. Accessed November 01, 2023 at: https://www.forschung-und-lehre.de/
- 10 Web of Science. Accessed February 08, 2024 at: https://www.webofscience.com/wos/
- 11 Szomszor M. The Web of Science Author Impact Beamplots: A new tool for responsible research evaluation. 01.03.2021 Accessed July 18, 2025 at: https://clarivate.com/academia-government/blog/the-web-of-science-author-impact-beamplots-a-new-tool-for-responsible-research-evaluation/
- 12 Adams J, McVeigh M, Pendlebury D. et al. Profiles, not metrics. January 2019. Accessed July 18, 2025 at: https://clarivate.com/academia-government/lp/profiles-not-metrics/
- 13 Yousaf R, Schmiede R. Barriers to women’s representation in academic excellence and positions of power. Asian J Ger Eur Stud 2017; 2: 2
- 14 O’Connell C, McKinnon M. Perceptions of Barriers to Career Progression for Academic Women in STEM. Societies 2021; 11: 27
- 15 Costello CA. Women in the Trenches: Barriers to Female Staff’s Advancement in Higher Education. Dissertations, Theses, and Masters Projects 2015.
- 16 Chao Q. The challenges facing female leaders in higher education – and how to address them. 12.02.2024 Accessed July 18, 2025 at: https://www.timeshighereducation.com/campus/challenges-facing-female-leaders-higher-education-and-how-address-them
- 17 Hirsch JE. An index to quantify an individual’s scientific research output. Proc Natl Acad Sci U S A 2005; 102: 16569-16572
- 18 Waltman L, van Eck NJ. The inconsistency of the h-index. JASIST 2012; 63: 406-415
- 19 Bornmann L, Marx W. Distributions instead of single numbers: Percentiles and beam plots for the assessment of single researchers. JASIST 2014; 65: 206-208
- 20 Bornmann L, Haunschild R. Plots for visualizing paper impact and journal impact of single researchers in a single graph. Scientometrics 2018; 115: 385-394